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As few studies have examined the relation between pubic hair grooming
and sexually transmitted infections (STIs), we took advantage of
nationally representative survey data to begin to explore this possible
association and to develop hypotheses for future prospective studies. In
our analysis, we observed a positive association between self-reported
pubic hair grooming and STI history, which we interpreted in several
poss...

As few studies have examined the relation between pubic hair grooming
and sexually transmitted infections (STIs), we took advantage of
nationally representative survey data to begin to explore this possible
association and to develop hypotheses for future prospective studies. In
our analysis, we observed a positive association between self-reported
pubic hair grooming and STI history, which we interpreted in several
possible ways given the limitations of our study (e.g., its cross-
sectional study design, self-reported assessment of grooming and STIs, and
lack of information on additional possible confounders, such as condom
use) Interpretations of our findings included: a) grooming-associated
epithelial microtears leading to increased risk of cutaneous STIs; b)
grooming-related protection against lice by pubic hair removal; c)
residual confounding by characteristics common to both grooming and STIs,
such as risky sexual behaviors; and d) what we believe is the most likely
interpretation, a combination of all of these explanations given our
differing magnitudes of association by type of STI. Based on these
interesting hypothesis-generating findings, we recommended that additional
epidemiologic studies be conducted with prospective data collection,
laboratory confirmation of STIs, and collection detailed STI risk
information to elucidate the mechanisms underlying our findings.

In response to Ojha and colleagues' concerns about confounding by
gender, race, income, and sexual frequency, we adjusted our analyses for
these variables: gender (male, female), race (White/Caucasian,
Black/African American, Hispanic/Latino, Mixed Races, or Other), income
(<$50,000, $50,000-74,999, $75,000-99,000, and >$100,000 USD), and
sexual frequency (daily, weekly, monthly, every three months or less). We
also repeated the analyses with and without survey weights. The
association between grooming and a history of STI remained (aOR= 1.71, 95%
CI 1.37-2.15). The other analyses yielded generally similar magnitudes of
association and the same inferences as the results presented in our
manuscript.

Notwithstanding these largely unchanged estimates, we believe that
residual confounding is still a possible interpretation of our findings
and encourage more research on this topic. However, even in the presence
of residual confounding, we would like to reinforce that use of grooming
as a marker of high-risk sexual behaviors may still have value for STI
prevention efforts to help identify individuals who would benefit most
from STI prevention counseling.

Osterberg et al. [1] assessed the association between pubic hair
grooming and sexually transmitted infections (STIs) using self-reported
data from a cross-sectional survey of adults aged 18 to 65 years in the
United States. The primary result was that individuals who reported ever-
grooming had 1.8 times the odds (odds ratio [OR]=1.8, 95% confidence
limits [CL]: 1.4, 2.2) of a history of STIs compared with individuals who...

Osterberg et al. [1] assessed the association between pubic hair
grooming and sexually transmitted infections (STIs) using self-reported
data from a cross-sectional survey of adults aged 18 to 65 years in the
United States. The primary result was that individuals who reported ever-
grooming had 1.8 times the odds (odds ratio [OR]=1.8, 95% confidence
limits [CL]: 1.4, 2.2) of a history of STIs compared with individuals who
reported never-grooming. The authors thus concluded that pubic hair
grooming is associated with a history of STIs. Nevertheless, these results
may be explained by confounding, selection, misclassification, and
protopathic (i.e. reverse causality) biases. We focus herein on unmeasured
confounding as an alternate explanation for the observed estimates.

The authors adjusted for age and number of sexual partners, but these
covariates are insufficient for adequately reducing confounding bias for
the exposure-outcome association of interest. Confounding pathways include
all common causes of exposure and outcome [2]. For example, gender
influences pubic hair grooming habits [3] and STIs [4], but gender was not
adjusted in the analysis by Osterberg et al. [1]. Therefore, gender is a
source of unmeasured confounding and the consequences may be nontrivial.

We used data reported by Osterberg et al. [1] for a sensitivity
analysis of unmeasured confounding using the following formula by Ding and
Vanderweele [5] to derive an adjustment factor,

(OReu*ORud)/(OReu+ORud-1)

where OReu is the odds ratio for the association between gender
(males as reference) and any grooming (OR=2.67), and ORud is the odds
ratio for the association between gender and STIs (OR=1.43). The observed
OR and corresponding CL (OR=1.8, 95% CL: 1.4, 2.2) are subsequently
divided by the adjustment factor (1.23), which results in an OR=1.5 (95%
CL: 1.1, 1.8) for the estimate after adjustment for gender and the
original covariates (age and number of sexual partners). The adjusted
estimate is attenuated from the authors' reported estimate and may be even
closer to the null if other relevant covariates could be adjusted such as
race/ethnicity and socioeconomic status. In addition, the authors reported
that the survey used sampling probability weights, but these weights did
not seem to be used in the analysis. The consequence is potential bias in
point estimates and overly narrow confidence limits [6], which raises
further questions about the authors' interpretation.

In summary, the interpretation by Osterberg et al. [1] may be based
on biased estimates. Greater attention to unmeasured confounding and other
sources of bias is warranted before attributing STIs to grooming habits.